Method for forming musical instrument bodies



y 1968 A. R. BRILHART 3,393,263

METHOD FOR FORMING MUSICAL INSTRUMENT BODIES Filed Feb. 26, 1965 INVENTOR Arnold R. Brilhcrr @MfWATTORNEYS United States Patent ()1 Bee 3,393,263 Patented July 16, 1968 ABSTRACT OF THE DISCLOSURE A unitary musical instrument body is formed by making core molds corresponding to sections of the musical instrument body, which sections collectively conform to the entire instrument body, forming a core in each of such molds, arranging and joining the cores so formed to constitute a replica of the core of the entire instrument body, and coating the replica so formed with a resin composition to form the instrument body. The cores are then removed by melting or dissolving them so as to leave the instrument body intact.

Background of the invention This invention relates to a method for forming musical instrument bodies, more particularly the bodies of woodwind or brass instruments.

In the production of brass musical instruments, many hours of precision fabrication are required for the process of converting brass tubing to the instrument body in its final form. The fabrication method includes drilling, forming, bending, swaging and soldering, all embodying techniques adapted over the years for the production of the particular brass instrument. In the boring and machining of woodwind instrument bodies, precision forming procedures are also necessary, with the additional caution taken that only properly aged wood be utilized in the case of the finer instruments. Where the woodwind body can be made of synthetics, this requirement is, of course, omitted; but the shaping, machining, finishing and like exacting procedures are still time-consuming and relatively expensive.

Summary of the invention The method described herein permits the economic fabrication of musical instrument bodies in a minimum of time and with a maximum of accuracy. The method obviates the necessity of having on hand the variety of machine tools formerly required for the fabrication of instrument bodies out of metal tubing or wood.

The method of the invention has for its object the forming of musical instrument bodies for instruments in the categories commonly denoted as woodwind or brass instruments. In the method a preformed, substantially permanent core mold is first produced, this mold duplicating accurately the bore of the musical instrument. An expendable core-forming metallic alloy is then poured into the core mold. The core-forming alloy has a melting point preferably in the range of from about 260 F. to about 280 F. The next step includes that of cooling the alloy, thus forming a core, the exterior surface and entire volume of which is a duplicate of the musical instrument bore. The core is then removed from the core mold; it is coated with a silicone release agent and then sprayed with a suitable resin, either a thermoplastic or preferably a thermosetting resin such as an epoxy, polyester or phenolic resin. The spraying procedure is continued until a layer of resin is built up upon the core equal to the thickness of the instrument body wall which is desired. Afterward, the resin coating is cured to a hardened state, thereby forming the instrument body. The core is removed by applying heat sufiicient to cause the core to melt and run out of the instrument body shell. The final steps comprise the machining and finishing of the body to the shape and dimensions of the selected musical instr-ument.

Brief description of the drawings In the drawings, FIG. 1 is a perspective partilly sectioned view of a core mold suitable for producing cores for use in the process of this invention.

FIG. 2 is a perspective view of a core duplicating the long bell section of a trumpet;

FIG. 3 is a cross-section of the core of FIG. 2 viewed along the line 33 thereof, and, in addition, having a coating of resinous material; and

FIG. 4 is a perspective view of a finished trumpet.

Description of preferred embodiments The first major step in the process of this invention is the preparation of a substantially permanent core mold. This mold will be used for the mass production of expendable musical instrument body cores; and it must therefore duplicate accurately the inside or bore of the instrument body. Since the mold will be used many times, the process of this invention actually comprises the steps subsequently described performed in conjunction with the preformed mold. Thus, there are two basic processes herein: production of a core mold together with subsequent steps for making the instrument body; and production of instrument bodies using the pre-formed core mold.

Although a number of molding techniques might be employed to produce the core mold, one such procedure, for example, would begin with a skilled pattern maker preparing a pattern of the selected instrument body. The pattern is made of wax, wood, plastic or the like and its size, surface area and cross-section must duplicate exactly the bore of the musical instrument, which for purposes of this description, is a standard B flat trumpet, shown complete in FIG. 4. The mold (shown in one embodiment 10 in FIG. 1) is prepared by a variety of methods, including shell molding techniques or conventional sand or plaster casting techniques. In the case of sand casting, a mixture 11 of a fine silica sand with a proper proportion of ad hesive is employed. The completed pattern of the instrument body (not shown) is placed in a flask 12 (a box-like container), and the sand mixture 11 is pounded around the pattern. A split mold may be produced by familiar techniques; and in fact this is the preferable form of the core mold, as it will enable removal of the cores without destruction of the mold. Sprue holes 13 and gates are provided as necessary. The sand mixture is allowed to set and the pattern is then removed and may be used to produce other similar molds. The finished mold resembles the embodiment shown in FIG. 1, the surface 14 of its cavity 15 duplicating the bore of the selected instrument body.

With the core mold completed, the process for actually producing instrument bodies may proceed. A core-forming material, such as a cerro-metal, is poured into the mold 10 through the sprue hole 13 until cavity 15 is curing temperature plus the exotherm of the resinous material.

In addition to cerro-metals, there are also available hotmelt water soluble plastic compounds which would be suitable for use herein. In the initial step (pouring the core-forming material into the mold these plastic materials are first melted and then poured, exactly like the cerro-metals. The advantage in their use lays in a later step of the process, melting out the core from the instrument body shell formed around it. Melting out is effected by dissolving the core in Water. The hot-melt plastics which could be employed herein have, for the most part, dimensional stability throughout the range of temperatures at which thermosetting resins may be cured, hence there is usually no problem of wrinkling or collapsing.

After the core-forming material has had sufficient time to set, the flasks 12 of mold 10 are split apart, and the core 16 is removed. As shown in FIG. 2, the core 16 has an extraneous sprue plug 17 which may or may not be removed depending upon the particular part of the instrument involved and whether or not it will affect the integrity of the finished part. A seam 18 is usually also present when a Split mold is used. It may be machined off if necessary.

A variety of parts of the instrument may be attached to the core 16. Braces 19, 20, lugs 21, 22 or key slots or bosses may be so attached as required. In FIG. 2, which shows the bell section of a B fiat trumpet, two braces 19 and 20 are secured to the core 16 by metal bands or fiber glass filaments 23. Braces 19, 20 will be secured to other spray-molded sections 24, of the trumpet when the finishing stage is reached (FIG. 4). The lugs 21, 22 are similarly attached to the core 16 and will later hold the valve assembly 26 securely in correct position. The parts attached to the core 16 may be made of metal, glass or a thermosetting plastic which is heat stable.

At this stage of the process, it is preferable to attach to core 16 the other expendable cores (not shown) of separately molded sections of the finished instrument body. Thus, referring to FIG. 4, the core sections molded to duplicate the curved portion 27 of the finished trumpet, the mouthpiece portion 24 and the straight tubular portion 25 as well as other core sections are secured to each other in the configuration of the finished instrument. By these means, the connected core sections duplicate the interior of the entire musical instrument.

A suitable resin is then evenly sprayed on the core 16 (and other core sections) until a plastic shell 28 of the desired uniform thickness is obtained. FIG. 3 shows a cross-section of the core 16 with a layer of plastic material 28 surrounding same. If desired, a silicone release agent may be sprayed upon the core 16. This will minimize air bubble formation and also produce smoother bores in the finished instrument. The resin which is sprayed on penetrates between the individual fibers of the fiber glass 23 used to secure the various attachments in place, and

thereby insures that these attachments will become integral parts of the shell 28 when it cures and hardens. When metal bands are employed to hold the attachments in position, they will preferably be perforated, thereby providing an increased surface area in contact with the thermosetting resin which is applied to the core 16. It might also be noted that the tendency of the metal band to break away from the shell 28 (subsequently the wall) of the instrument body can be minimized by selecting metal bands and resinous material the coetficients of expansion of which are nearly the same.

The resin utilized may be a thermosetting resin such as an epoxy, a polyester or a phenolic; or it may be a thermoplastic resin dispersion system such as nylon, a polypropylene or a polycarbonate. A thermosetting resin is preferable to a thermoplastic resin, however, because the latter will not produce instrument bodies of optimum vibration characteristics. Whatever the resin employed, it may be suitably pigmented if that is desired. A particularly eflicacious plastic material for use herein is a thermosetting resin containing glass filament rovings. The spray-on process utilizing this mixture, although somewhat more complex than that which uses pure plastic, is fairly straightforward: a spray apparatus is employed which will thoroughly mix the glass rovings, curing catalyst and resin just prior to its ejection from the sprayer nozzle.

After spraying is complete and a coating of the desired uniform thickness is obtained, it may first be smoothed over, and is then hung in an oven to cure. Curing temm peratures will of course vary, depending upon the type of thermosetting resin used; but for a particular resin, the cure will likely be effected within a range of from about 140 F. to 250 F. The cure time also varies, depending upon the type of resin and catalyst, and upon the size and thickness of the part. Usually up to 16 hours are required for the cure.

With a cure temperature likely to be approximately 240-250 F., one should select a cerro-metal melting at from 260-280 F. for the production of cores. The temperature is also well within a safe operating limit above which (over 300 F.), the plastic might deteriorate.

When the shell 28 is properly cured, the oven temperature is increased (to 280 F. for example) and the cerrometal core 16 is thereby melted out. The melted metal may be recovered and re-used. If hot-melt water soluble plastics are used to form the core, the core is simply washed out of the shell 28 with a stream of water. The hardened and cured plastic shell 28 constitutes a section 29 of the finished instrument (a B fiat trumpet) 30 shown in FIG. 4. When necessary, the section so formed may be finished by removing spurs and rough spots. Although the interior or bore of the section is identical with that of the original pattern, the exterior of the section 29 may have to be machined slightly to match its exterior with that of a prototype musical instrument.

Saxophones, clarinets and flutes can also be made according to the method of this invention, with the provision for tone holes being made by the pattern maker. A tone hole would appear as a raised circular portion on the core. When spraying on the resin, these raised portions Would be avoided; and after the coated material has hardened and the core material melted out, the tone holes may be reamed out with ease and subsequently machined to a smooth finish.

I claim:

1. A method of making a unitary musical instrument body for a woodwind or brass instrument having a bore through which a column of air passes, comprising:

(a) forming a plurality of core molds, each corresponding to a section of such musical instrument body and having an inner surface which duplicates the bore of the section to which it corresponds. such that all of said sections collectively conform to the entire musical instrument body;

(b) pouring an expendable core-forming material into each of said core molds to form a core therein upon solidification of said core-forming material;

(c) arranging and joining the cores so formed to comprise a replica of the bore of such musical instrument;

((1) coating the replica formed by said cores with a resin composition and heating the coated replica so formed to cure said resin composition, thereby forming an instrument body, the temperature at which such cure is carried out being lower than the melting temperature of the core-forming material;

(e) removing said cores from the instrument body;

and

(f) machining and finishing said instrument body to the shape and dimensions of such musical instrument.

2. A method of making a unitary musical instrument body for a woodwind or brass instrument having a bore through which a column of air passes, comprising:

(a) forming a plurality of core molds, each corresponding to a section of such musical instrument body and having an inner surface which duplicates the bore of the section to which it corresponds, such that all of said sections collectively conform to the entire musical instrument body;

(b) pouring an expendable core-forming material into each of said core molds to form a core therein upon solidification of said core-forming material;

(c) arranging and joining the cores so for-med to comprise a replica of the bore of such musical instrument;

(d) afiixing such braces, lugs, key slots and bosses to said cores, at predetermined places thereon, as are required by such instrument body and fastening them to said cores by means of flexible elongated fasteners wound around the cores, said flexible elongated fasteners having substantially the same coeflicient of thermal expansion as the instrument body and having sufiicient surface area to bond securely to the instrument body;

(e) coating the replica formed by said cores, including the flexible elongated fasteners fastening the braces, lugs, key slots and bosses to said cores, with a resin composition and heating the coated replica so formed to cure said resin composition to form such instrument body, the temperature at which such cure is carried out being lower than the melting temperature of the core-forming material;

(f) removing said cores from the instrument body;

and

(g) machining and finishing said instrument bod-y to the shape and dimensions of such musical instrument.

3. A method of making a unitary musical instrument body for a woodwind or brass instrument as defined in claim 2 wherein said flexible elongated fasteners are fiber glass filaments.

4. A method of making a unitary musical instrument body for a woodwind or brass instrument as defined in claim 2 wherein said flexible elongated fasteners are metal bands having adequate surface area to bond securely to said resin composition.

5. A method of making a unitary musical instrument body for a woodwind or brass instrument as defined in claim 2 wherein said cores are formed to contain raised circular portions at locations where tone holes are desired, there being substantially no resin composition applied to said raised circular portions during coating of said replica, thereby forming such tone holes in the instrument body.

6. A method of making a unitary musical instrument body for a woodwind or brass instrument as defined in claim 2 wherein said resin composition is a glass-filled thermosetting resin.

7. A method of making a unitary musical instrument body for a woodwind or brass instrument as defined in claim 2 wherein said core-forming material is water soluble and wherein the solidified cores are removed from the instrument body by dissolving the cores in water.

8. A method of making a unitary musical instrument body for a woodwind or brass instrument as defined in claim 2 wherein said core-forming material is a metallic alloy and in which the solidified cores are removed from the instrument body by melting them at a temperature higher than the curing temperature of the resin composition.

9. A method of making a unitary musical instrument body for a woodwind or brass instrument as defined in claim 2 wherein the resin composition is a thermoplastic resin selected from the group consisting of nylon, polypropylene and polycarbonate resins.

10. A method of making a unitary musical instrument body for a woodwind or brass instrument as defined in claim 2 wherein the resin composition is a thermosetting resin selected from the group consisting of epoxy, polyester and phenolic resins.

References Cited UNITED STATES PATENTS 720,482 2/ 1903 Richards. 1,604,274 10/1926 Gammeter. 1,656,312 1/1928 Black. 2,345,977 4/ 1944 Howard et a1. 264-219 2,972,779 2/1961 Cowley 264162 3,222,738 12/ 1965 Carter 264-221 3,326,269 6/ 1967 Schneider 10638.9

JAMES A. SEIDLECK, Primary Examiner.

DONALD J. ARNOLD, Examiner.

I. E. THURLOW, Assistant Examiner. 

